Can you double check /etc/nginx/sites-available/default to make sure the following was entered was entered without any typos?

  location ~ \.php$ {
        try_files $uri =404;
        fastcgi_split_path_info ^(.+\.php)(/.+)$;
        fastcgi_pass unix:/var/run/php5-fpm.sock;
        fastcgi_index index.php;
        fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
        include fastcgi_params;
    }

Also, you do need to make sure Nginx is restarted for those updates to take effect.

sudo service nginx restart

Happy coding,

Jon Schwenn
Platform Support Specialist
DigitalOcean